Abstract: 【Objective】 The aim of this experiment was to study the preparation of Astragalus polysaccharide liposomes (APSL) and their transport in Caco-2 cell model. 【Method】 APSL was prepared by film dispersion method，the structure of APSL was observed by transmission electron microscopy，and the encapsulation rate and drug loading capacity of liposomes were detected by the method of fisetin. A Caco-2 monolayer cell model was established，and the structure was observed by transmission electron microscopy. The denseness and completeness of the Caco-2 cell model was evaluated by measuring the cell resistance value and apparent permeability coefficient (Papp) of sodium fluorescein，respectively. Transmembrane transport experiments were performed from the apical side (AP) to the basolateral side (BL) and from the BL to the AP side to analyze the effects of drug concentration，and P-gp inhibitor Verapamil (Ver) on the transport. 【Result】 The encapsulation rate of APSL was 71.74%±4.87%，the drug loading was 2.92%，the spherical bilayer structure was visible under transmission electron microscopy，the particle size was (126.6±0.283) nm (n=3)，and the polymer dispersity index (PDI) was 0.190±0.009. Caco-2 cells were observed to be tightly bound under transmission electron microscopy，forming a microvillus structure，and the transmembrane resistivity value reached 650 Ω·cm²，the alkaline phosphatase (ALP) ratio reached 3.05，and the Papp of sodium fluorescein was 1.96×10^-7 cm/s，which fulfilled the requirements of the transport experiments. At different concentrations (75，150 and 300 μg/mL)，the efflux ratio (ER) of APS was higher than 1.5，and the ER of APSL was lower than 1.5. The Papp of the APSL group was extremely significantly higher than that of APS group in the absorption direction of AP-BL at three concentrations (P＜0.01)，and the ER was lower than that of APS group. After adding P-gp protein inhibitors，compared with APS group，the Papp of APS+Ver group was extremely significantly increased in the AP-BL direction (P＜0.01)，while the ER was decreased. However，there was no significant change in Papp on both sides of APSL+Ver group (P＞0.05). Compared with the ER of APS group (3.995)，the ER of APSL group (1.005) was decreased.【Conclusion】 APS was poorly transported on the monolayer model of Caco-2 cells in vitro as a low-permeability compound，and there might be P-gp protein exocytosis，whereas APSL was able to increase the transport and absorption of APS，and improve the permeability of the drug.

Key words: Astragalus polysaccharide liposome; Caco-2 cell model; absorption characteristics